Method and apparatus for cathode sputtering using a cylindrical cathode



April 18, 1967 Filed Nov. 28, 1962 u 3, R CATHODE SPUTTERING USING ACYLINDRICAL CATHODE 3 Sheets-Sheet ,1.

INVENTOR fiaj Lama 222 ATTORNEY Aprll 18, 1967 G. LUNSFORD 3,314,873

METHOD AND APPARATUS FOR CATHODE SFUTTERING USING A CYIJINDRICAL CATHODE3 Sheets-Shes t :9

Filed Nov. 28, 1962 INVENTOR 6x5 fizaasyazzg zufir- NNv ATTORNEY3,314,873 SPU'ITERING USING DE 3 Sheets-Sheet .3

Aprll 18, 1967 LUNSFO METHOD AND APPARATUS FOR CATHO A CYLINDRICAL CATHOi 119d Nov 28 1962 O D 0 D O Q P Q 0 O O C O D O O INVENTOR 6 214.9.Zwmyard ATTORNEY United States Patent ()fihce 3,3l4,873 Patented Apr.18, 1967 3 314 873 METHOD AND APPAR ATlJS FOR CATHGDE SIlUT- TERINGUSING A CYLINDRICAL CATHODE Gus Lunsford, Winston-Salem, N.C., assignorto Western Electric Company, Incorporated, New York, N.Y., a corporationof New York Filed Nov. 28, 1962, Ser. No. 240,599 6 Claims. (Cl.204-192) This invention relates to a method of and apparatus forsputtering and more particularly to an in-line cathodic sputteringmethod and apparatus for continuously and uniformly depositingelectrically conductive coatings on electrical components. Thisinvention finds special utility in sputtering conductive terminations onresistors of the type including a non-conductive core on which aconductive film is deposited, for example, a conventional depositedcarbon resistor.

metal, consists of some type of stationary anode and cathode mountedwithin an evacuated bell jar which defines a sputtering chamber. Forexample, see US. Patent 3,039,952. The productive output of this type ofapparatus is limited due to several, inherent physical characteristicsof such apparatus. First, the bell jar sputtering chamber does notconveniently accommodate an efiicient system for introducing andretrieving an article from the chamber without destroying the vacuum.Thus, rapid, continuous operation of hell jar sputtering chamber isdifficult to attain. Secondly, the bell jar system, and like systems,place serious limitations on the configuration of the cathode and anodewhich may be employed in a sputtering chamber of practical size.Increased production on such equipment, involves costly multiplicationof bell jars, each with separate cathode, anode, evacuation, and articlesupporting facilities. Finally, the usual cathode and anodeconfigurations in bell jar systems produce an ion field which issuitably uniform in so limited an area as to render batch sputteringimpractical. The usual bell jar system is designed to accommodate asingle article,.thus reducing the productivity of the apparatus.

It is an object of the present invention to provide a new and improvedcathodic sputtering machine.

It is another object of this invention to provide an improved sputteringmachine and method for continuously and uniformly depositing conductivematerial on a plurality of components passing therethrough.

It is a further object of this invention to provide a new and improvedtubular anode configuration suitable for coating a serial procession ofworkpieces.

It is another object of this invention to provide a sputtering chamberwhich is effectively of infinite electrical length and which providesuniform deposition of metal on a workpiece.

It is another object of this invention to provide new and improvedapparatus for continuously conveying a plurality of articles through anevacuated chamber for coating the articles with a film of material.

With these and other objects in mind, this invention contemplates asputtering method and apparatus for coating articles with material. Forexample, the articles may be deposited carbon resistor blanks, and goldthe to be sputtered and means for supporting an article to be coatedwithin the cathode. The supporting means, may, for example, comprise acontinuous conveyor.

Also provided are means for causing the material of the cathode tosputter and coat the supported article.

In a specific embodiment of this invention, the means for supportingarticles to be coated may comprise a conveyor which also serves as theanode for causing the cathode to sputter. In a further refinement, thesesupporting means may perform four functions, that of: a conveyor, ananode, a mask for preventing unwanted sputtering, and a seal to preventundesirable leakage of gases into the tubular cathode.

Other objects and advantages of the invention will become apparent fromthe following detailed description and the accompanying drawingsillustrating a specific embodiment thereof, in which:

FIG. 1 is an exploded, sectional view of a deposited carbon resistor,the terminations of which have been produced by a machine according tothis invention;

FIG. 2 is a plan view of an embodiment of this invention showing asputtering chamber, a serially connected plurality of locks sealing theends of the chamber, and a chain type conveying system extending throughthe chamber FIG. 3 illustrates one link of the conveyor chain shown inFIG. 2, partially loaded with articles to be coated;

FIG. 4 is an elevation, partially in section, of the apparatus of FIG.2, showing details of the locks, the sputtering chamber, and apparatusfor evacuating the locks and chamber;

FIG. 5 is an enlarged, fragmentary, sectional view of one of the locksillustrated in. FIG. 4 showing a look including lined sealing tubesthrough which articles to be coated are conveyed;

FIG. 6 is an which may be expeditiously produced of the sputtering 22 onwhich a conductive carbon The above-mentioned terminatrons, terminations27, gold in this instance, are sputtered contact with caps 28. Finally,a spiral cut is made in the carbon coating 23, thereby determining theelectrical resistance between the leads 29, and the resulting resistorcomponent is encapsulated. The purpose of terminations conductivesurface on which to fix caps 28.

Hereinafter, a ceramic core 22 having a carbon coating 23 depositedthereon will be referred to as a core 30.

of cores 30 is transported from feed tube 33 into alignment with apusher 43. Pusher 43 is provided with a plurality of pins 44 which alignwith apertures 34 when shuttle 41 is in its rightmost position (FIG. 2).Actuation of pusher 43 drives the group of cores from shuttle 41 intotransverse bores in a link 45 of a conveyor chain 48. A back-stop 49insures proper positioning of the cores in the link 45.

Each link 45 in chain 48 is identical to that illustrated in FIG. 3.Link 45 includes an elongated body 51 having a plurality of parallel,longitudinally spaced, transverse bores 52 therein. The sides of thesebores 52 provide a means for uniformly orienting the cores 32 andprovide the cores with uniform spacing along body 51. Body 51 is milledto define a groove 53 at one end and a tongue 54 at the other endthereof. Vertical bores 56 and 57 extend through the bifurcationsdefining groove 53 and through tongue 54, respectively. Each link 45 isprovided with transverse aligning bores 58 and 59 engageable withaligning pins on pusher 43 to insure precise alignment of pusher 43 withthe link. Chain 48 is made up of links 45 placed end to end intongue-in-groove relation with wrist pins (not shown) in the bores 56and 57.

Chain 48 forms a closed loop which passes over hexagonal idler wheel 61and is tensioned by idler wheel 62. Each of the six sides of the idlerwheels is of a length to accommodate a link 45 and is relieved toaccommodate cores 30. The idler wheels 61 and 62 are fixed to shafts 63and 64, respectively, which are mounted for rotation on a base 65 (FIG.4).

Since the above-described feeding operation occurring at feeding station31 is intermittent, it is necessary to impart an intermittent,stop-pause-go, motion to chain 48 in time with the operation of pusher43. Such a drive may be accomplished in any of many known ways. A verydesirable drive is one which successively engages each link 45 and movesit precisely the length of the link, then returns to engage the nextlink and move it the same distance, and so on. Control means (not shown)coordinate feeding operations at feeding station 31 with theintermittent drive, so that each link 45 pauses for loading in alignmentwith pusher 43.

Chain 48 loaded with cores 30 passes about idler wheel 62 between therolls of roller guide 81, through a series of vacuum chambers 82, 83,and 84; through sputtering chamber 85; and through vacuum chambers 86,87, and 88. On leaving vacuum chamber 88, the chain passes throughunloading station 90 where the cores 30 having terminations 27 (FIG. 1)sputtered thereon are unloaded in preparation for the above-outlinedsubsequent fabricating operations. The chain 48 is then guided by therolls of roller guide 91 onto idler wheel 61. From the idler wheel 61,the chain passes through a safety unloading and chain cleaning station92, thence to feeding station 31 where it is reloaded with cores 30.

Referring to FIG. 4, each of the vacuum chambers 82-84 and 86-88 isidentical to vacuum chamber 82 and includes an elongated cylindricalchamber 101 having a hollow stem 102 extending radially therefrom.Chamber 101 is provided at its ends with flanges 103 and 104, and stem102 is provided with flange 106. Flanges 103 and 104 are sealed againstpartitions 111-118, respectively. Each stem 102 is sealed by means ofits flange 106 onbase 65.

Base 65 is apertured at each of the points over which a stern 102 issealed. Tubes 121, 122, and 123 extend through these apertures tocommunicate with vacuum chambers 82, 83, and 84, respectively. Likewise,tubes 126, 127, and 128 communicate with vacuum chambers 86, 87, and 88,respectively. Tubes 121 and 128 are connected to a vacuum pump 131;tubes 122 and 127 are connected to a vacuum pump 132, and, tubes 123 and126 are connected to a vacuum pump 133. Pumps 131-133 are powered bymotors 136, 137, and 138, respectively. Pump 131 is adjusted to producea high degree of evacuation in the vacuum chambers to which it isconnected;

4 pump 132 a somewhat higher degree chambers to which it is connected;and pump 133 higher degree of evacuation in its chambers.

As seen in FIG. 4, each of partitions 111, 112, and 113, 116, 117, and118 has a lock 141 extending therethrough. Partitions 114 and areapertured to communicate with the interior of accordion couplings 142and 143, respectively, and the accordion couplings are sealed tosputtering chamber 85. Thus, the vacuum chambers communicate with oneanother, and vacuum chambers 82 and 88 communicate with the atmosphereonly through locks 141. Also, the sputtering chamber is isolated fromthe atmosphere by these locks.

Referring to FIGS. 5 and 6, each lock 141 comprises a pair ofsymmetrically arranged lock tubes 146 and 147 provided, respectively,with flanges 148 and 149. The lock tubes are sealed by means of theseflanges over an aperture in each partition, shown, for example, asaperture 151 in partition 111. The length of each lock 141 is preferablyas long as a link 45. As a minimum it should be sufficiently long as tobridge a plurality of bores 52 in a link 45.

As best seen in FIG. 6, each loc'k tube 146 and 147 is made up of anupper channel 156 and a lower channel 157 which together define a tunnel158 of rectangular cross section. A liner 161 is placed within tunnel158. The liner, formed by mating upper and lower halfs 162 and 163, ismade of fluorocarbon material such as Teflon, which has aself-lubricating quality. The halfs of liner 161 together define apassage 166, shaped to conform to the cross section of a link 45 havingcores 30 loaded therein. In this example, passage 166 has a friction fitabout chain 48 and provides a .003 to .005 inch clearance about the coreends.

Referring to FIG. 7, sputtering chamber 85 includes a hollow cylindricalcathode sealed at its ends by a pair of end caps 182 and 184. In thisexample, the cathode has an inside diameter of approximately 1% inchesand is about 10 inches long. The cathode is provided with a liner 186 ofthe material to be sputtered, gold in this example, which covers itsentire interior and extends through apertures in end caps 182 and 184.Cool= ing fins 187 project radially from the cathode. A pair of shields191 and 192 are spaced symmetrically about end caps 182 and 184,respectively. A pair of ring seals 196 and 197 of a resilient,electrically insulating, heat resistant material, such as siliconerubber, seal end caps 182 and 184 within shields 191 and 192. The ringseals provide electrical insulation and prevent the intrusion ofatmosphere between the caps and the shields.

Accordion coupling 142 is sealed over an aperture 193 in shield 191.Likewise, accordion coupling 143 is sealed over an aperture 194 inshield 192. These couplings, being freely extendible, accommodate anythermal expansion of the sputtering chamber, and facilitate access tothe interior of sputtering chamber 85.

Referring to FIG. 7, cathode 180 may be negatively biased by potentialsource 206, the positive side of which is grounded. Chain 48 and shields191 and 192 are also grounded. Thus, cathode 180 may be maintained at anegative potential relative to the chain 48 and to the shields 191 and192, both the chain and the shield serving as anodes.

The interior of cathode 180 may be sufiiciently evacuated by means ofthe above-described pumps and maintained at a suflicient negativepotential relative to chain 48 to create a cathode dark space 211 offinite thickness (FIG. 8). Chain 48, loaded with cores 30 passes throughcathode 180 at a point removed from the center of the cathode and spacedfrom liner 186 by a margin greater than the thickness of dark space 211.

While the cores 30 are within the sputtering chamber, material from theliner 186 sputters onto the cores in the areas not masked by links 45.

After terminations 27 have been sputtered on the cores,-

of evacuation in the a still the cores pass through accordion coupling143, and through vacuum chambers 86, '87, and 88 to be automaticallyunloaded at unloading station 90.

Operation The general mode of operation of a machine according to thisinvention has been described above in tracing the course in cores 30from feeding station 31 to unloading station 90. Certain details of theoperation of this machine require further explanation.

In order to prepare the above-described machine for operation, it isnecessary to take certain steps. Motors 136, 137, and 138 must beenergized to drive pumps 131, 132, and 133 and evacuate the vacuumchambers and sputtering chamber to the proper degree. Initially, vacuumchambers 84 and 86 should be maintained at a pressure on the order ofone micron of mercury; vacuum chambers 83 and 87 on the order to twomicrons of mercury; and vacuum chambers 82 and 88 on the order of fivemillimeters of mercury.

Potential source 206 must be activated to charge inches), this maycathode to a potential and 192 and chain 48.

With the cathode potential so adjusted, argon is permitted to leakthrough conduits 171 and 172 (FIG. 4) until sputtering occurs on thesurface of liner 186. The drive for chain 48, feeding station 31, andunloading station 92 are activated and the above-described core feedingoperation commences carrying cores 30 through the vacuum chambers, locks141, and sputtering chamber 85.

When a link 45 enters a lock 141 (FIG. 6), passage 166 very closelysurrounds the contour of the link and the core (in the above example,friction fit about the chain, and a .003-.005 inch clearance about thecore.

Such close clearance provides a blocking action which inhibits the flowof gas through the lock tube. It does this by sharply blocking passage166 and also by creating a turbulance about the core and link whichfurther inhibits the flow of gases through gases by blocking the passageand by increasing the above-mentioned turbulent effect. In a link 45carrying a large number of cores, this combined blocking and turbulencecreation provides especially efiective seal against the escape of gases.Increased turbulence, and hence reduction of gas flow, is accomplishedat each partition 111-118 due to the etTect of passage 151 (FIG. 5)which is larger in diameter than passage 166.

Each link 45' performs at least four separate functions in cooperationwith the elements of this machine. It serves as a conveyor of cores 30,an anode in the sputtering operation, a mask to prevent coating thecores except on preselected areas; and means for preventing theintrusion of gases through locks 141.

Cylindrical cathode 180 surrounds the cores supported on chain 48.Tl'llS configuration permits the achievement of sputtering many timestional, plate type cathode. Also, since sputtering material is directedinwardly from the walls of the cathode, the deposition of sputteredmaterial on the cores is very uniform. Furthermore, it is unnecessary torevolve the cores in order to achieve uniform coating thereon.

While it would be feasible to have the cores pass through the center ofthe cathode rather than along the off center path as described above, itis advantageous to use an olT center path (FIG. 8) for a number ofreasons. The focusing effect of the cylindrical cathode would causeextreme heating of the anode and the core if the latter passed throughthe center of the cathode. if sutficiently intense, may actually preventeffective coat ing by sputtering. In using such a cylindrical cathode,there is an area between the center of the cathode and the inner marginof the cathode dark space where maximum deposition occurs. This pointhas been determined expermentally and is reflected in spacing the pathof chain 48 from the center of cathode and from the dark space 211 asshown in FIG. 8.

Since the entire interior of the sputtering chamber, accordioncouplings, and vacuum chamber is in a highly evacuated condition, andsince the cathode is charged negatively relative to the remainingportions of the ma chine, there would, in the absence of shields 191 and192, be a tendency to sputter and deposit material at points other thanWithin the cathode. Shields 191 and 192 are placed sufiiciently close tothe cathode to be within the cathode dark space thereof. Thiseffectively prevents the sputtering of material outside the confines ofthe cathode.

It is to be understood that the above-described arrange ment ofapparatus and construction of elemental parts are simply illustrative ofan application of the principles of this invention and that many othermodifications may be made without departing from the invention.

What is claimed is: 1. A method of coating articles by cathodic whichcomprises the steps of:

applying a sputteringpotential between a cylindrical cathode having acircular cross-section and a major axis and to an anode positionedtherewithin, and

moving articles to be coated through said cathode along a path which isparallel to and removed from both said major axis and the walls of saidcathode so that no portion of said articles impinges upon said majoraxis.

2. A method of coating articles by cathodic sputtering which comprisesthe steps of:

applying a sputtering potential to a cylindrical cathode having acircular cross-section and a major axis and to a movable conveyorpositioned therewithin, mounting articles on said conveyor,

moving said conveyor and said mounting articles through said cathodealong a path which is parallel to and removed from said major axis andthe walls of said cathode, and

maintaining said moving conveyor so that no portion of said articlesimpinges upon said major axis.

3. A method of coating articles by sputtering utilizing a cylindricalcathode having a circular cross-section and a major axis which comprisesthe steps of:

mounting articles to a movable conveyor,

positioning said conveyor within said cathode parallel to said majoraxis so as to preclude the impingement of said mounted articles uponsaid major axis,

Such heating,

sputtering said conveyor whereby heating of said articles is minimizedand the sputtering rate is maximized.

4. In a sputtering machine for coating articles with material,

a tubular cathode of the material to be sputtered, the cathode having acircular cross section and a major axis,

an anode positioned within the cathode,

means for moving the anode along a predetermined and means forcathodically sputtering said material to coat unmasked portions of theoriented articles.

5. In a sputtering machine for coating articles with material,

(a) a sputtering chamber open on at least one end,

(b) a tubular cathode of said material to be sputtered within saidchamber, the cathode having a circular cross section and a major axis,

(c) means for supporting articles to be coated within said cathode andfor sealing said open end of said chamber, said supporting and sealingmeans includ- (1) a conveyor extending through said cathode fortransporting a plurality of said articles along a predetermined path ina uniformly oriented configuration spaced along said path, the pathbeing longitudinal and parallel to and removed from both said major axisand the walls of said cathode so that no part of said articles or ofsaid supporting means impinges upon said major axis, and

(2) a tube of length greater than the article spacing maintainable bysaid conveyor, said tube defining a passage which surrounds saidconveyor and has a cross section corresponding to the cross sectiontaken through both the conveyor and an article loaded therein, and

((1) electric potential-producing means, including said cathode and saidconveyor, for impressing a negative potential on said cathode and apositive potential on said conveyor to cathodically sputter saidmaterial and coat said supported articles.

6. In a sputtering machine for coating articles with material,

(a) a sputtering chamber opened at both ends, said chamber containing acylindrical cathode of the material to be sputtered, the cathode havinga circular cross section and a major axis,

(b) at least one vacuum chamber positioned at and connected to one endof said sputtering chamber, (c) at least one vacuum chamber positionedat and connected to the other end of said sputtering chamber,

(d) means including an anode and said cathode, for producing a cathodedark space having a predetermined thickness dimension within saidcathode, said anode including a conveyor extending through saidcylindrical cathode and through said vacuum chambers for (1)transporting said articles in a uniformly oriented configuration spacedalong a path, said path being removed from said major axis of saidcathode and at a distance from the walls of said cathode greater thansaid predetermined thickness dimension so that said articles aretransported parallel to said major axis and so that no portion of saidarticles or of said anode impinges upon said major axis, and (2) maskingportions of said articles, and (c) a series of locks sealing each ofsaid vacuum chambers, each lock including a tube having a length greaterthan the spacing between said articles, said tube defining a passagewhich surrounds said conveyor and has a cross section corresponding tothe cross section taken through both the conveyor and an article loadedtherein.

References Cited by the Examiner UNITED STATES PATENTS OTHER REFERENCESHolland: Vacuum Deposition of Thin Films, Chapman & Hall, London, 1956,page 420.

JOHN H. MACK, Primary Examiner. R. MIHALEK, Assistant Examiner.

1. A METHOD OF COATING ARTICLES BY CATHODIC SPUTTERING WHICH COMPRISESTHE STEPS OF: APPLYING A SPUTTERING POTENTIAL BETWEEN A CYLINDRICALCATHODE HAVING A CIRCULAR CROSS-SECTION AND A MAJOR AXIS AND TO AN ANODEPOSITIONED THREWITHIN, AND MOVING ARTICLES TO BE COATED THROUGH SAIDCATHODE ALONG A PATH WHICH IS PARALLEL TO AND REMOVED FROM BOTH SAIDMAJOR AXIS AND THE WALLS OF SO THAT NO PORTION OF SAID ARTICLES IMPINGESUPON SAID MAJOR AXIS.
 5. IN A SPUTTERING MACHINE FOR COATING ARTICLESWITH MATERIAL, (A) A SPUTTRING CHAMBER OPEN ON AT LEAST ONE END, (B) ATUBULAR CATHODE OF SAID MATERIAL TO BE SPUTTERED WITHIN SAID CHAMBR, THECATHODE HAVING A CIRCULAR CROSS SECTION AND A MAJOR AXIS, (C) MEANS FORSUPPORTING ARTICLES TO BE COATED WITHIN SAID CATHODE AND FOR SEALINGSAID OPEN END OF SAID CHAMBER, SAID SUPPORTING AND SEALING MEANSINCLUDING, (1) A CONVEYOR EXTENDING THROUGH SAID CATHODE FORTRANSPORTING A PLURALITYOF SAID ARTICLES ALONG A PREDETERMINED PATH IN AUNIFORMLY ORIENTED CONFIGURATION SPACED ALONG SAID PATH, THE PATH BEINGLONGITUDINAL AND PARALLEL TO AND REMOVED FROM BOTH SAID MAJOR AXIS ANDTHE WALLS OF SAID CATHODE SO THAT NO PART OF SAID ARTICLES OR OF SAIDSUPPORTING MENS IMPINGES UPON SAID MAJOR AXIS, AND (2) A TUBE OF LENGTHGREATER THAN THE ARTICLE SPACING MAINTAINABLE BY SAID CONVEYOR, SAIDTUBE DEFINING A PASSAGE WHICH SURROUNDS SAID CONVEYOR AND HAS A CROSSSECTION CORRESPONDING TO THE CROSS SECTION TAKEN THROUGH BOTH THECONVEYOR AND AN ARTICLE LOADED THEREIN, AND (D) ELECTRICPOTENTIAL-PRODUCING MEANS, INCLUDING SAID CATHODE AND SAID CONVEYOR, FORIMPRESSING A NEGATIVE POTENTIAL ON SAID CATHODE AND A POSITIVE POTENTIALON SAID CONVEYOR TO CATHODICALLY SPUTTER SAID MATERIAL AND COAT SAIDSUPPORTED ARTICLES.